1. Field of the Invention
This invention relates to a flexible tube for an endoscope and an electronic endoscope equipped with the flexible tube.
2. Description of the Prior Art
A medical endoscope is used in medical procedures for diagnosing and treating diseases. This type of medical endoscope includes an elongated insertion portion which is to be inserted into a body cavity (tubular cavity). The insertion portion is formed into an elongated tubular shape having a hollow space through which medical instruments such as an optical fiber, electrical cable, mechanical cable, tubes and the like are inserted and arranged. Further, except for the tip portion thereof, the insertion portion is constructed from a flexible tube for an endoscope (hereinafter, simply referred to as xe2x80x9cflexible tubexe2x80x9d or xe2x80x9cflexible insertion tubexe2x80x9d depending on occasions) having a prescribed flexibility (elasticity).
The endoscope is used by inserting the insertion portion deep into a body cavity, for example, the stomach, duodenum, small intestine or large intestine. When inserting the insertion portion of the endoscope into the body cavity, the flexible tube (insertion portion) is advanced into the body cavity by applying a push-in force or a twist to the base end (proximal side) of the flexible tube.
However, the flexible tube for an endoscope is quite long and needs to bend along the curves of the body cavity during insertion. Therefore, even when an inserting operation force such as a push-in force and twist is applied thereto, the flexible tube experiences a lot of resistance due to such factors as friction with the inner walls of the body cavity and the like. For this reason, it is not easy to advance the tip portion thereof into the body cavity. Because the operation for inserting the flexible tube into a body cavity is difficult as described above, there has been a need for a flexible tube that can be more easily inserted into a body cavity.
It is an object of the present invention to provide a flexible tube for an endoscope that has excellent operability so as to be easily inserted into a body cavity.
In order to achieve the above object, the present invention is directed to a flexible tube for an endoscope which comprises an elongated flexible tubular body and a plurality of easily bendable portions provided in the tubular body in a spaced apart manner along the longitudinal direction thereof. Each of these easily bendable portion is adapted to be bent locally with a smaller curvature radius when the flexible tube is bent in one direction.
According to the flexible tube for an endoscope of the present invention described above, since the resistance that the flexible tube receives from the inner walls of a body cavity when being advanced is reduced, it becomes possible to easily insert the flexible tube for an endoscope deep into the interior of the body cavity. Accordingly, the flexible tube for an endoscope of the present invention has excellent insertion operability.
In a preferred embodiment of the present invention, the average interval between the adjacent easily bendable portions is in the range 50-400 mm. This makes it possible to further improve the insertion operability.
Further, in the preferred embodiment of the present invention, when the average of the curvature radius of each of said easily bendable portions is defined as R1 and the curvature radius of the center portion lying between said adjacent easily bendable portions is defined as R2, the value of the ratio R1/R2 in the bending state lies in the range of 0.2-0.9. This also improves the insertion operability.
In the present invention, the flexible tubular body is preferably constructed from a core body having a hollow space and an ouster cover which is provided over the outer periphery of the core body, and the outer cover being formed into either of a single layer structure or a laminated structure having a plurality of layers.
In this case, it is preferred that each of said easily bendable portions is formed by locally changing the flexural rigidity of the outer cover. This makes it possible to realize a flexible tube for an endoscope having excellent insertion operability with a simple structure which can be easily manufactured.
Further, in the preferred embodiment, at least one of said easily bendable portions is formed by changing the thickness of at least one layer of the laminated structure of the outer cover at a position corresponding to the easily bendable portion. According to this, it is possible to form the easily bendable portions easily.
Alternatively, in the preferred embodiment, at least one of said easily bendable portions may be constructed from a portion of the outer cover where the thickness of the outer cover changes along the circumferential direction. This also makes it possible to form the easily bendable portions easily.
In the present invention, it is preferred that the outer cover has a portion which is made of a material including at least one kind of material selected from the group consisting of polyurethane-based elastomer, polyester-based elastomer, polyolefin-based elastomer, polystyrene-based elastomer, polyamide-based elastomer, and fluoro-based elastomer. Use of such a material makes it possible to improve characteristics required for a flexible tube for an endoscope.
Preferably, the outer cover is applied over the core body using an extrusion molding method. This makes it possible to manufacture the flexible tube with high productivity.
Further, preferably, the core body includes a coil formed by winding a band-shaped material into a spiral and a braided tube provided over the outer periphery of the coil and formed by braiding fine wires. This makes it possible to have sufficient mechanical strength.
In another preferred embodiment of the present invention, at least one of said easily bendable portions is formed by forming the outer cover so as to have an elliptical cross section at a position corresponding to the easily bendable portion.
Further, in other preferred embodiment of the present invention, at least one of said easily bendable portions can be formed by increasing the winding pitch of the coil locally at a position corresponding to the easily bendable portion. Furthermore, at least one of said easily bendable portions may be formed by reducing the width and/or thickness of the band-shaped material of the coil 21 locally at a position corresponding to the easily bendable portion.
Another aspect of the present invention is directed to an electronic endoscope which comprises an operation section which is operated by an operator and a flexible tube for an endoscope which is connected to the operation section. The flexible tube includes an elongated flexible tubular body and a plurality of easily bendable portions provided in the tubular body in a spaced apart manner along the longitudinal direction thereof. Each of these easily bendable portion is adapted to bend locally with a smaller curvature radius when the flexible tube is bent in one direction.
These and other objects, structures and results of the present invention will be apparent more clearly when the following detailed description of the preferred embodiments is considered taken in conjunction with the accompanying drawings.